/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.tomcat.util.http.fileupload;

import org.apache.tomcat.util.http.fileupload.util.mime.MimeUtility;

import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

/**
 * A simple parser intended to parse sequences of name/value pairs.
 * <p>
 * Parameter values are expected to be enclosed in quotes if they
 * contain unsafe characters, such as '=' characters or separators.
 * Parameter values are optional and can be omitted.
 * <p>
 * <p>
 * <code>param1 = value; param2 = "anything goes; really"; param3</code>
 * </p>
 */
public class ParameterParser {

	/**
	 * String to be parsed.
	 */
	private char[] chars = null;

	/**
	 * Current position in the string.
	 */
	private int pos = 0;

	/**
	 * Maximum position in the string.
	 */
	private int len = 0;

	/**
	 * Start of a token.
	 */
	private int i1 = 0;

	/**
	 * End of a token.
	 */
	private int i2 = 0;

	/**
	 * Whether names stored in the map should be converted to lower case.
	 */
	private boolean lowerCaseNames = false;

	/**
	 * Default ParameterParser constructor.
	 */
	public ParameterParser() {
		super();
	}

	/**
	 * Are there any characters left to parse?
	 *
	 * @return {@code true} if there are unparsed characters,
	 * {@code false} otherwise.
	 */
	private boolean hasChar() {
		return this.pos < this.len;
	}

	/**
	 * A helper method to process the parsed token. This method removes
	 * leading and trailing blanks as well as enclosing quotation marks,
	 * when necessary.
	 *
	 * @param quoted {@code true} if quotation marks are expected,
	 *               {@code false} otherwise.
	 * @return the token
	 */
	private String getToken(boolean quoted) {
		// Trim leading white spaces
		while ((i1 < i2) && (Character.isWhitespace(chars[i1]))) {
			i1++;
		}
		// Trim trailing white spaces
		while ((i2 > i1) && (Character.isWhitespace(chars[i2 - 1]))) {
			i2--;
		}
		// Strip away quotation marks if necessary
		if (quoted
				&& ((i2 - i1) >= 2)
				&& (chars[i1] == '"')
				&& (chars[i2 - 1] == '"')) {
			i1++;
			i2--;
		}
		String result = null;
		if (i2 > i1) {
			result = new String(chars, i1, i2 - i1);
		}
		return result;
	}

	/**
	 * Tests if the given character is present in the array of characters.
	 *
	 * @param ch      the character to test for presense in the array of characters
	 * @param charray the array of characters to test against
	 * @return {@code true} if the character is present in the array of
	 * characters, {@code false} otherwise.
	 */
	private boolean isOneOf(char ch, final char[] charray) {
		boolean result = false;
		for (char element : charray) {
			if (ch == element) {
				result = true;
				break;
			}
		}
		return result;
	}

	/**
	 * Parses out a token until any of the given terminators
	 * is encountered.
	 *
	 * @param terminators the array of terminating characters. Any of these
	 *                    characters when encountered signify the end of the token
	 * @return the token
	 */
	private String parseToken(final char[] terminators) {
		char ch;
		i1 = pos;
		i2 = pos;
		while (hasChar()) {
			ch = chars[pos];
			if (isOneOf(ch, terminators)) {
				break;
			}
			i2++;
			pos++;
		}
		return getToken(false);
	}

	/**
	 * Parses out a token until any of the given terminators
	 * is encountered outside the quotation marks.
	 *
	 * @param terminators the array of terminating characters. Any of these
	 *                    characters when encountered outside the quotation marks signify the end
	 *                    of the token
	 * @return the token
	 */
	private String parseQuotedToken(final char[] terminators) {
		char ch;
		i1 = pos;
		i2 = pos;
		boolean quoted = false;
		boolean charEscaped = false;
		while (hasChar()) {
			ch = chars[pos];
			if (!quoted && isOneOf(ch, terminators)) {
				break;
			}
			if (!charEscaped && ch == '"') {
				quoted = !quoted;
			}
			charEscaped = (!charEscaped && ch == '\\');
			i2++;
			pos++;

		}
		return getToken(true);
	}

	/**
	 * Returns {@code true} if parameter names are to be converted to lower
	 * case when name/value pairs are parsed.
	 *
	 * @return {@code true} if parameter names are to be
	 * converted to lower case when name/value pairs are parsed.
	 * Otherwise returns {@code false}
	 */
	public boolean isLowerCaseNames() {
		return this.lowerCaseNames;
	}

	/**
	 * Sets the flag if parameter names are to be converted to lower case when
	 * name/value pairs are parsed.
	 *
	 * @param b {@code true} if parameter names are to be
	 *          converted to lower case when name/value pairs are parsed.
	 *          {@code false} otherwise.
	 */
	public void setLowerCaseNames(boolean b) {
		this.lowerCaseNames = b;
	}

	/**
	 * Extracts a map of name/value pairs from the given string. Names are
	 * expected to be unique. Multiple separators may be specified and
	 * the earliest found in the input string is used.
	 *
	 * @param str        the string that contains a sequence of name/value pairs
	 * @param separators the name/value pairs separators
	 * @return a map of name/value pairs
	 */
	public Map<String, String> parse(final String str, char[] separators) {
		if (separators == null || separators.length == 0) {
			return new HashMap<String, String>();
		}
		char separator = separators[0];
		if (str != null) {
			int idx = str.length();
			for (char separator2 : separators) {
				int tmp = str.indexOf(separator2);
				if (tmp != -1 && tmp < idx) {
					idx = tmp;
					separator = separator2;
				}
			}
		}
		return parse(str, separator);
	}

	/**
	 * Extracts a map of name/value pairs from the given string. Names are
	 * expected to be unique.
	 *
	 * @param str       the string that contains a sequence of name/value pairs
	 * @param separator the name/value pairs separator
	 * @return a map of name/value pairs
	 */
	public Map<String, String> parse(final String str, char separator) {
		if (str == null) {
			return new HashMap<String, String>();
		}
		return parse(str.toCharArray(), separator);
	}

	/**
	 * Extracts a map of name/value pairs from the given array of
	 * characters. Names are expected to be unique.
	 *
	 * @param charArray the array of characters that contains a sequence of
	 *                  name/value pairs
	 * @param separator the name/value pairs separator
	 * @return a map of name/value pairs
	 */
	public Map<String, String> parse(final char[] charArray, char separator) {
		if (charArray == null) {
			return new HashMap<String, String>();
		}
		return parse(charArray, 0, charArray.length, separator);
	}

	/**
	 * Extracts a map of name/value pairs from the given array of
	 * characters. Names are expected to be unique.
	 *
	 * @param charArray the array of characters that contains a sequence of
	 *                  name/value pairs
	 * @param offset    - the initial offset.
	 * @param length    - the length.
	 * @param separator the name/value pairs separator
	 * @return a map of name/value pairs
	 */
	public Map<String, String> parse(
			final char[] charArray,
			int offset,
			int length,
			char separator) {

		if (charArray == null) {
			return new HashMap<String, String>();
		}
		HashMap<String, String> params = new HashMap<String, String>();
		this.chars = charArray;
		this.pos = offset;
		this.len = length;

		String paramName = null;
		String paramValue = null;
		while (hasChar()) {
			paramName = parseToken(new char[]{
					'=', separator});
			paramValue = null;
			if (hasChar() && (charArray[pos] == '=')) {
				pos++; // skip '='
				paramValue = parseQuotedToken(new char[]{
						separator});

				if (paramValue != null) {
					try {
						paramValue = MimeUtility.decodeText(paramValue);
					} catch (UnsupportedEncodingException e) {
						// let's keep the original value in this case
					}
				}
			}
			if (hasChar() && (charArray[pos] == separator)) {
				pos++; // skip separator
			}
			if ((paramName != null) && (paramName.length() > 0)) {
				if (this.lowerCaseNames) {
					paramName = paramName.toLowerCase(Locale.ENGLISH);
				}

				params.put(paramName, paramValue);
			}
		}
		return params;
	}

}
